Tuesday, September 17, 2013

On warm summer nights, some central Arizona neighborhoods are visited by these princes (and princesses) in disguise, Sonoran Desert Toads (Incilius alvarius). The New River corridor is a popular stretch of habitat for these wide-mouthed, warty amphibians. Although the adults are terrestrial, and content to spend most of the year in burrows that may be miles from any water, permanent or temporary ponds are necessary for reproduction.

They will take advantage of nearly any water source we provide for them, intentionally or unintentionally, to re-hydrate. Dog dishes, bird baths and shallow steps of swimming pools are perfect places to sit for a while and fatten up after a long winter below ground. Toads imbibe water through their skin, especially through a special "drinking patch" on their belly and hind legs. A few hours sitting in a mud puddle can make the difference between a "full" toad and a skinny toad. Although many folks regard them as pests, because they are also quite toxic, especially to dogs that harass them, having a few toads around can serve as effective pest management, since they will eat huge quantities of insects.

Toad scat is dry and ashy, essentially the keratinous remains of the insects they have eaten. This large sample of toad scat is compared to my ring; it's as thick as my finger, but not gooey at all. If you step on it, the turd turns to dust and blows away on the wind. Just another fun little nature tidbit for you!

Tuesday, September 3, 2013

This elegant and docile looking nectivorous wasp is also a vicious predator who will slay spiders more than twice her size in order to insure the success of her children. Also known as a tarantula hawk or spider wasp (Pepsis thisbe), these huge wasps grow up to two inches (5 cm) long from the powerful jaws to the tip of their glossy black abdomen. Females can be identified by the curled tips of their antennae, while male antennae are straight. Both are commonly seen sipping nectar from a variety of flowers, and are especially fond of milkweeds. But only the female possesses a sharp stinger and the instinct to use it to deliver powerful neurotoxins to stun food for her offspring. Unless you harass her, there is very little chance that a tarantula hawk would attack a human. But if you are a tarantula, she will chase you down.

We were fortunate to witness the aftermath of such a biochemical attack along the Upper Salt River last weekend. While walking along the road to our camp, we noticed a tarantula splayed out in the dirt. I poked it with my toe, but it didn't move. Within moments, a tarantula hawk started circling the spider, so I stepped away, and she landed on top of it and began to drag it up the hillside. We think she must have already delivered the neurotoxin that effectively paralyzes the prey, and was returning to retrieve it once it was completely immobilized. Unperturbed by our presence, we watched as she pulled the spider up beneath a rock. A single egg will be buried with the zombified spider, providing nutrition for wasp larvae as it develops into a two inch long grub, eating the spider alive as it grows. After the larvae has had its fill, it will pupate and remain in a resting stage underground for several months before emerging as an adult wasp.

I like knowing that for every tarantula wasp, there was once a big hairy tarantula walking the earth. We see a lot of wasps around, so that must mean that there are is an equally healthy population of tarantulas in the neighborhood.

Welcome to Kat Tracks

On the suburban fringe, one foot is in wild untamed places and the other is in landscapes changed by human desires. I'm interested in understanding the threads of natural history that weave the two together. Join me in Kat Tracks as I explore the suburban fringe of Phoenix, Arizona. Some of these posts are also found in my companion blog, Natural History of Deem Hills.

Wild Kat

As a naturalist with a special interest in botany and plant ecology, some of my greatest passions are to explore, photograph and write about native plants. If I can spark an awareness or interest in natural history in others along the way, that is my greatest reward.